Antenna measurements require that the antenna under test (AUT) is illuminated by a uniform plane wave. This requirement is generally achieved in the far field for a range length greater than 2D2/λ where D is the largest dimension of the AUT. In many cases particularly for very short λ this will dictate large distances. A compact range creates a plane wave field at distances considerably shorter than those needed under conventional far-field criteria. The required compact range is usually so short that the implementation can be accomplished indoors. In the compact range a uniform plane wave is generated by a large parabolic reflector with high surface accuracy. Room reflections are minimised by using absorbing material on the walls.
The classic way to align an antenna to the electrical co-ordinate system of an antenna measurement range is to do this alignment with the AUT mounted to the stable antenna tower at the measurement range to then determine the positioning of AUT in relation to the electrical co-ordinate system of the measurement range.
A problem with this classical way of measurement set-up is for instance that while the often time-consuming alignment is performed the quite expensive antenna measurement range will be occupied and can not be used for other antenna measurements. Since the antenna often also is mounted at a great height it is then complicated to achieve the desired accurate determination of the co-ordinates.
Therefore, there is a desire to simplify, as well as if possible speed up, this setting up procedure for the antenna to be tested, which has led to a new inventive method now disclosed by the present patent application.